errno.h

errno.h 是C语言C标准函式库里的标头档，定义了透过错误码来回报错误资讯的宏：

　　errno宏定义为一个int型态的左值, 包含任何函式使用errno功能所产生的上一个错误码。

　　一些表示错误码，定义为整数值的宏：

　　EDOM 源自于函式的参数超出范围,例如sqrt(-1)

　　ERANGE 源自于函式的结果超出范围,例如strtol("0xfffffffff",NULL,0)

　　EILSEQ 源自于不合法的字符顺序,例如wcstombs(str, L"\xffff", 2)

　　查看错误代码errno是调试程序的一个重要方法。当linux C api函数发生异常时,一般会将errno变量(需include errno.h)赋一个整数值,不同的值表示不同的含义,可以通过查看该值推测出错的原因。在实际编程中用这一招解决了不少原本看来莫名其妙的问题。比较 麻烦的是每次都要去linux源代码里面查找错误代码的含义，现在把它贴出来，以后需要查时就来这里看了。

　　以下来自linux 2.4.20-18的内核代码中的/usr/include/asm/errno.h

　　

#ifndef _I386_ERRNO_H　　#define _I386_ERRNO_H　　#define EPERM 1 /* Operation not permitted */　　#define ENOENT 2 /* No such file or directory */　　#define ESRCH 3 /* No such process */　　#define EINTR 4 /* Interrupted system call */　　#define EIO 5 /* I/O error */　　#define ENXIO 6 /* No such device or address */　　#define E2BIG 7 /* Arg list too long */　　#define ENOEXEC 8 /* Exec format error */　　#define EBADF 9 /* Bad file number */　　#define ECHILD 10 /* No child processes */　　#define EAGAIN 11 /* Try again */　　#define ENOMEM 12 /* Out of memory */　　#define EACCES 13 /* Permission denied */　　#define EFAULT 14 /* Bad address */　　#define ENOTBLK 15 /* Block device required */　　#define EBUSY 16 /* Device or resource busy */　　#define EEXIST 17 /* File exists */　　#define EXDEV 18 /* Cross-device link */　　#define ENODEV 19 /* No such device */　　#define ENOTDIR 20 /* Not a directory */　　#define EISDIR 21 /* Is a directory */　　#define EINVAL 22 /* Invalid argument */　　#define ENFILE 23 /* File table overflow */　　#define EMFILE 24 /* Too many open files */　　#define ENOTTY 25 /* Not a typewriter */　　#define ETXTBSY 26 /* Text file busy */　　#define EFBIG 27 /* File too large */　　#define ENOSPC 28 /* No space left on device */　　#define ESPIPE 29 /* Illegal seek */　　#define EROFS 30 /* Read-only file system */　　#define EMLINK 31 /* Too many links */　　#define EPIPE 32 /* Broken pipe */　　#define EDOM 33 /* Math argument out of domain of func */　　#define ERANGE 34 /* Math result not representable */　　#define EDEADLK 35 /* Resource deadlock would occur */　　#define ENAMETOOLONG 36 /* File name too long */　　#define ENOLCK 37 /* No record locks available */　　#define ENOSYS 38 /* Function not implemented */　　#define ENOTEMPTY 39 /* Directory not empty */　　#define ELOOP 40 /* Too many symbolic links encountered */　　#define EWOULDBLOCK EAGAIN /* Operation would block */　　#define ENOMSG 42 /* No message of desired type */　　#define EIDRM 43 /* Identifier removed */　　#define ECHRNG 44 /* Channel number out of range */　　#define EL2NSYNC 45 /* Level 2 not synchronized */　　#define EL3HLT 46 /* Level 3 halted */　　#define EL3RST 47 /* Level 3 reset */　　#define ELNRNG 48 /* Link number out of range */　　#define EUNATCH 49 /* Protocol driver not attached */　　#define ENOCSI 50 /* No CSI structure available */　　#define EL2HLT 51 /* Level 2 halted */　　#define EBADE 52 /* Invalid exchange */　　#define EBADR 53 /* Invalid request descriptor */　　#define EXFULL 54 /* Exchange full */　　#define ENOANO 55 /* No anode */　　#define EBADRQC 56 /* Invalid request code */　　#define EBADSLT 57 /* Invalid slot */　　#define EDEADLOCK EDEADLK　　#define EBFONT 59 /* Bad font file format */　　#define ENOSTR 60 /* Device not a stream */　　#define ENODATA 61 /* No data available */　　#define ETIME 62 /* Timer expired */　　#define ENOSR 63 /* Out of streams resources */　　#define ENONET 64 /* Machine is not on the network */　　#define ENOPKG 65 /* Package not installed */　　#define EREMOTE 66 /* Object is remote */　　#define ENOLINK 67 /* Link has been severed */　　#define EADV 68 /* Advertise error */　　#define ESRMNT 69 /* Srmount error */　　#define ECOMM 70 /* Communication error on send */　　#define EPROTO 71 /* Protocol error */　　#define EMULTIHOP 72 /* Multihop attempted */　　#define EDOTDOT 73 /* RFS specific error */　　#define EBADMSG 74 /* Not a data message */　　#define EOVERFLOW 75 /* Value too large for defined data type */　　#define ENOTUNIQ 76 /* Name not unique on network */　　#define EBADFD 77 /* File descriptor in bad state */　　#define EREMCHG 78 /* Remote address changed */　　#define ELIBACC 79 /* Can not access a needed shared library */　　#define ELIBBAD 80 /* Accessing a corrupted shared library */　　#define ELIBSCN 81 /* .lib section in a.out corrupted */　　#define ELIBMAX 82 /* Attempting to link in too many shared libraries */　　#define ELIBEXEC 83 /* Cannot exec a shared library directly */　　#define EILSEQ 84 /* Illegal byte sequence */　　#define ERESTART 85 /* Interrupted system call should be restarted */　　#define ESTRPIPE 86 /* Streams pipe error */　　#define EUSERS 87 /* Too many users */　　#define ENOTSOCK 88 /* Socket operation on non-socket */　　#define EDESTADDRREQ 89 /* Destination address required */　　#define EMSGSIZE 90 /* Message too long */　　#define EPROTOTYPE 91 /* Protocol wrong type for socket */　　#define ENOPROTOOPT 92 /* Protocol not available */　　#define EPROTONOSUPPORT 93 /* Protocol not supported */　　#define ESOCKTNOSUPPORT 94 /* Socket type not supported */　　#define EOPNOTSUPP 95 /* Operation not supported on transport endpoint */　　#define EPFNOSUPPORT 96 /* Protocol family not supported */　　#define EAFNOSUPPORT 97 /* Address family not supported by protocol */　　#define EADDRINUSE 98 /* Address already in use */　　#define EADDRNOTAVAIL 99 /* Cannot assign requested address */　　#define ENETDOWN 100 /* Network is down */　　#define ENETUNREACH 101 /* Network is unreachable */　　#define ENETRESET 102 /* Network dropped connection because of reset */　　#define ECONNABORTED 103 /* Software caused connection abort */　　#define ECONNRESET 104 /* Connection reset by peer */　　#define ENOBUFS 105 /* No buffer space available */　　#define EISCONN 106 /* Transport endpoint is already connected */　　#define ENOTCONN 107 /* Transport endpoint is not connected */　　#define ESHUTDOWN 108 /* Cannot send after transport endpoint shutdown */　　#define ETOOMANYREFS 109 /* Too many references: cannot splice */　　#define ETIMEDOUT 110 /* Connection timed out */　　#define ECONNREFUSED 111 /* Connection refused */　　#define EHOSTDOWN 112 /* Host is down */　　#define EHOSTUNREACH 113 /* No route to host */　　#define EALREADY 114 /* Operation already in progress */　　#define EINPROGRESS 115 /* Operation now in progress */　　#define ESTALE 116 /* Stale NFS file handle */　　#define EUCLEAN 117 /* Structure needs cleaning */　　#define ENOTNAM 118 /* Not a XENIX named type file */　　#define ENAVAIL 119 /* No XENIX semaphores available */　　#define EISNAM 120 /* Is a named type file */　　#define EREMOTEIO 121 /* Remote I/O error */　　#define EDQUOT 122 /* Quota exceeded */　　#define ENOMEDIUM 123 /* No medium found */　　#define EMEDIUMTYPE 124 /* Wrong medium type */　　#end